This application relates to a removable film for providing an aerodynamically clean surface on airfoils.
Gas turbine engines are known and, typically, include a fan delivering air into a compressor. In an aircraft application, the fan will deliver air into a bypass duct defined inwardly of a nacelle in addition to the air delivered into the compressor. Air from the compressor is delivered into a combustion section where it is mixed with fuel and ignited. Products of this combustion pass downstream over turbine rotors driving them to rotate.
Historically, a turbine rotor has driven a fan rotor at a same speed. More recently, it has been proposed to insert a gear reduction between the turbine rotor and the fan. With the movement to the gear reduction, the fan may now rotate at slower speeds to provide reduced levels of fan pressure ratio while increasing the outer diameter of the fan blades dramatically. With this increase, a bypass ratio or the ratio of air delivered into the bypass duct compared to the volume of air delivered into the compressor has increased.
With this enlarged fan, laminar or near laminar aerodynamic design and other approaches for reduced fan duct aerodynamic loss becomes more important. However, surfaces of the fan, associated vanes, the nacelle, and inlet into the nacelle, etc. can deteriorate due to dirt, impacted insects or other airborne debris.
It has been proposed to wash these surfaces, however, this has not always removed all of the accumulated material. In addition, the impact of debris can cause small areas of damage to surface finish or component profile which, alone, or in combination with accumulated debris, may lead to local disturbances in the aerodynamic properties and degradation away from a laminar flow.
It is known to have a removable layer of thin adhesive film that can be removed once the cumulated dirt has been built up on an outer layer of the film. This type film has been utilized on the windows of race cars as an example. Removable film has also been proposed for the windshields of aircraft.
Existing automotive applications also include the use of such film to prevent or minimize paint damage from impacting debris.